The present invention relates to a composition and a method for controlling reaction pressures during the foaming process resulting in an easily flame retarded foam-in place insulation.
The present invention is the subject of an Invention Disclosure Document filed Feb. 4, 1980, Disclosure Document No. 087883.
Rigid plastic foams have been widely utilized as thermal insulating materials, light construction materials, and floating materials because of their excellent properties. However, since they are composed of plastic materials they can provide a substantial fuel contribution, cause rapid flame spread and produce a great deal of noxious smoke on thermal decomposition when burned or heated to an elevated temperature, thus leading to their limited use as construction material.
With the present invention in conserving heating fuel, many existing buildings are having additional insulation added to their structures, and newly constructed buildings are including more insulation then was formerly used.
A most commonly used type of insulation for existing structures is ureaformaldehyde foam, which is foamed in place between the outside wall and the inside wall of the structure. Unfortunately, the ureaformaldehyde foam can break down releasing noxious formaldehyde fumes. Some jurisdictions have already prohibited the use of ureaformaldehyde foams in buildings because of the potential continual long term release of formaldehyde vapors.
Another type of material used for insulation is polyurethane foam. However, polyurethane foam provides a substantial fuel contribution, spreads flame rapidly, and releases toxic gases including but not by way of limitation gases such as carbon monoxide carbon dioxide, and hydrogen cyanide when burned. Additionally, polyurethane foam generally disintegrates when burned. Polyurethane foam cannot be used to retrofit existing structures with in-wall insulation due to the high reaction pressures generated during the foaming process which can be sufficient to separate the wallboard from the wall studs.
Rigid polyurethane foams are generally prepared by reacting an organic polyisocyanate with a polyol in the presence of a foaming agent surfactant and catalyst. In order to reduce the cost of preparing these foams, efforts have been made to employ starch as a polyol reactant in the preparation of urethane foams. The use of starch directly has been unsatisfactory because of the poor physical properties of the foam which results. Oxyalkylated starch yields satisfactory foams, but the direct oxyalkylation of starch results in degradation or decomposition of the starch and a product which is not uniform in chemical or physical properties.
A satisfactory process for utilizing starch as a component in the preparation of polyurethane foams is disclosed in U.S. Pat. No. 3,277,213. In this process, starch is added to a polyhydric alcohol containing at least two hydroxyl groups in a proportion equivalent to at least 0.5 mole of the alcohol per mole of glucose unit weight of starch in the presence of an acid catalyst. The resulting mixture is then oxyalkylated to yield a polyether polyol suitable for use in preparating polyurethane foams of excellent physical properties. Although it is generally recognized that the presence of high proportions of nitrogen, phosphorus, and/or chlorine atoms enhances the flame resistance of urethane foams, present techniques for adding these components to urethane foams are not entirely satisfactory.
U.S. Pat. No. 3,674,717, discloses a process for preparing flame-retardant polyurethane foams by admixing starch with phosphoric acid at an elevated temperature and oxyethylating the resulting mixture to yield a starch-phosphorus-based polyether useful as a reactant in the preparation of urethane foams with flame-retardant properties.
Another method of making flame retardant polyurethane foams, as disclosed in U.S. Pat. No. 3,658,731, is by reacting dry whey or lactose and whey or yeast protein with a polyisocyanate in the presence of dimethylsulfoxide.